The present invention relates to a lens holder and a lens protector for use in an optical pick-up.
As optical information-recording media, a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, and a DVD-RW are known. The optical pick-up of these apparatuses for performing a focus control and a tracking control detects information by converging light beams which have passed through an objective lens on a disc surface. Thus to form an image on the disc surface, it is necessary to focus the light beams thereon by compensating defocusing caused by deflection of the disc. If there is a deviation (radial deviation of optical axis) between a signal track (bit string of information) on the disc and the optical axis of the objective lens, information cannot be correctly read. Thus it is necessary to make the optical axis of the objective lens coincident with the signal track by compensating the deviation of the signal track.
Because the capacity and density of an optical disc has increased greatly in recent years, a work space has become small. That is, the clearance between the objective lens and the disc surface has become short when a focus servo is in operation. Consequently the danger of a collision between the objective lens and the optical disc has increased. Owing to a much increase in the capacity and density of the optical disc, a protection layer covering the signal-recording layer of the optical disc has become thinner. Therefore the conventional optical pick-up has a problem that owing to the collision between the objective lens and the optical disc, the signal-recording layer of the optical disc is liable to be damaged.
To solve the problems, attempts have been made as disclosed in Japanese Patent Application Laid-Open No. 2002-222535. In the disclosure, a coating layer made of fluoro resin is formed on the surface, of the lens holder holding the objective lens, which confronts the optical disc. Thereby when the focus servo is not in operation, the optical disc collides with the coating layer before the optical disc collides with the objective lens. Thereby it is possible to prevent the objective lens from colliding with the optical disc and the optical disc from being damaged.
The lens holder holding the objective lens is made of injection-molded synthetic resin. A product formed by injection-molding the synthetic resin has burrs formed on a parting line thereof, a contact portion thereof which contacts a ejector pin, and a gate thereof. The burrs formed on the product are rubbed off. Powder generated from the burrs are scattered in the apparatus such as the CD-ROM, thus damaging the optical disc or causing a failure.
Heretofore barrel polishing is used to remove the burr from the lens holder. However, the barrel polishing has a problem that an objective lens-mounting hole and a bearing hole are liable to be clogged with media.
When the lens holder is formed by injection molding, it has an unfavorable surface configuration on the periphery of the gate. That is, the lens holder has a large flatness. It is unpreferable to set the gate on the lens holder at a position of the surface confronting the optical disc. It is unpreferable to set the gate on the surface, of the lens holder, on which a coating layer is formed. When the gate is formed on the rear surface of the lens holder, the mark of the ejector pin remains on the surface of the lens holder over which the coating layer is formed.